Whew - it's nice to be able to actually talk about this at last!
It has taken many months of concentrated team effort - in our personal time since we are not employees of Paradox, even though they are publishing the game - to come up with what I am happy to opine is a fun, reasonably 'historical/realistic' and flexible game.
As Lennart said, this will be covered in a future Dev.Diary, but I think you'll like the result.
For now I'll just say that one feature is that land combat takes longer to resolve - and the bigger the forces the longer it takes. This means that reallocation of units, feeding in of reinforcements and application of air power to key points all becomes feasible before the issue is decided. Units on 'support defence' orders will usually get into action before the initial line is retreating. Taking Poland now typically takes me around 4-6 weeks; in one memorable game the battle for Warsaw took 28 days, with reinforcements being fed in by both sides and the rest of the German operation developing all around it and air support added (well, attempted) by both sides, before the city finally fell.
That sounds great. The long combat systems have proven to be the best model for this game that I have played. It was implimented in the Starfire/MEM system a while back largely by increasing Org. However, that did not actually solve the problem of the dogpiling effect. Sounds like maybe you have a handle on that.
You are right, one thing it does do is increase the potency of "support defence", and this does help to increase the potency of defense, but it does not truly replicate the innate advantage of defense. Why defense is stronger IRL is a complicated issue, but it is generally an axiom that all other things being equal, attackers need to outnumber defenders by a 3 to 1 ratio to have any hope of success.
In vanilla HOI on plains, defenders only really have the 20% dug in bonus, which means basically that attackers only have to exceed defenders by a factor of 1.2 to achieve success.
Another defensive advantage in HOI is the fact that retreating units gain org, while attacking ones lose it. This can be used to create a cushion effect as attackers come forward. Unfortunately, though that only applies in MP, since the AI units gain org while moving.
In the EIR system addition to playing with Org and defensive values to draw out battles, I increased defensive strength simply by increasing the frequency of defensive combat events, and I think that is the only true way using the vanilla HOI system to give defenders proper bonuses.
But there are a few hidden things that I have discovered that should be accounted for in all long combat systems.
Terrain:
As I mentioned, the vanilla terrain bonuses need to be adjusted. The vanillas set up can be a problem for a number or reasons, one being the potential for map bottlenecks to appear at important points. The entry way into France through Belgium is a significant case here, with woods and rivers all over. Against a human France difficult to overcome, unless terrain bonuses are modified to decrease those bonuses.
Another serious bottleneck occurs at Bilbao/Dax in Spain, should someone choose to go that route.
Durruti on the MEM mod team artfully adjusted the map used in MEM to give a little more room for manouver in these areas, and that is also the map I used for EIR. That and adjusting terrain bonuses down has been effective.
The good side is of course that if you increase defensive potential we can get more accurate historical results, such as the one I noted above, the Ukraine can be defended, and Germany can potentially launch an attack over the Baltic river systems and woods, and directly east toward Smolensk.
Thus the Russian player does not have to resort to the ahistorical and gamey trick of defending the Dnepr river, and waiting for the onslaught 500 km behind the border.
Support defense:
The AI SD proportions need to be adjusted down, because the AI will throw way more units than it needs into battles, and because it does not cycle units as a human player does by retreating them and replacing them with appropriate reinforcements, these useless no org units sit in the battle taking damage for no purpose, and more and more units are drawn into battle. As well, (and in some ways worse) on long fronts like the Russian front the AI will bunch up its units creating convenient conglomerations of units without proper flank protection that can be easily pocketed.
So if this is not dealt with it appears that the AI is defending better, but really it is not. It hangs on in individual provinces for longer, but the whole front collapses at about the same rate, or even worse, because it is actually sacrificing whole divisions, which is expensive. It's kind of like a standfast order for the ai.
This means that manpower losses to AI countries are increased, and manpower has to be adjusted everywhere. At the same time a happy medium for their "Support Defense" ratio has to be found and applied to each AI country file. Its a pain in the ass.
The advantage of your position is that you could just apply a new default through the exe. What I did was install a generic AI switch for all countries that triggered at game start, reducing the SD proportion from the default of .33, and setting it to .2 for all AI countries.
What would be really fine is if you could get the AI to retreat divisions that have no org -- I think that would be a huge AI improvement, simple but with tremendous impact, since the AI would be cycling units through the front.
Those were my observations and discoveries with modding vanilla HOI II. Things to consider.
I am really looking forward to what you guys are doing, as I think the main aspect of the HOI II system that really needed fixing was the combat system, and it sounds like you guys are coming at it from the right direction.
